1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to multimedia streaming, and more particularly, to variably transmitting a multimedia stream according to requirements of a client device and the state of a channel.
2. Description of the Related Art
Related art demand for technology to provide a stream of multimedia contents in real time through a network has been increasing. When this technology is applied to a wireless network, there are difficulties due to the characteristics of the wireless network environments. To achieve high-quality video streaming, one may consider the issues of wireless bandwidth fluctuation, multipath fading, contending traffic, etc. Therefore, transmitting multimedia on a wireless network requires robustness against a partial data loss due to packetization of a video frame and against a high packet error rate. In addition, it may also be necessary to support mutually different types of client devices in consideration of their respective characteristics in order to achieve high-quality video streaming. Furthermore, as the user demand for client devices supporting a high resolution increases, the need for stable multimedia transmission guaranteeing the video quality becomes greater and greater.
FIG. 1 is a block diagram illustrating the configuration of a related art transceiver supporting adaptive channel control (U.S. Pat. No. 6,005,851). A transceiver receives a data packet from a data source/sink. The transceiver includes a dispatcher 20, which outputs data to channel controllers 24a to 24e through data lines 22a to 22e. The dispatcher 20 is connected for two-way communication with the channel controllers 24a to 24e through control lines 26a to 26e. The dispatcher 20 is connected for two-way communication with a sync controller 30 through a control line 28. The channel controllers 24a to 24e are coupled for two-way communication with a packet send and receive unit (PSRU) 34. Each of the channel controllers 24a to 24e also has a data output line connected to a multiplexer (MUX) 35. The MUX 35 output, in turn, outputs data to the data source/sink.
In FIG. 1, virtual channels for each data type (e.g., video, graphics, text) are created and mapped onto the physical channels based on a priority assigned to each virtual channel. Also, each virtual channel is allocated a quality of service (QoS), and each channel controller 24a to 24e is allocated to each virtual channel. These channel controllers 24a to 24e are connected to the dispatcher 20, which receives a stream of data packets and distributes the data packets to the channel controllers 24a to 24e based on the virtual channels which are allocated to the channel controllers 24a to 24e. 
When any one of the channel controllers 24a to 24e encounters degradation in a transmission which reduces QoS below a specified value, a QoS parameter is adjusted. If this action does not achieve the specified QoS, the corresponding channel controller warns the dispatcher 20. Upon receipt of the warning, the dispatcher 20 reduces the corresponding channel controller's specified QoS or another channel's QoS, depending on the data type. When the dispatcher 20 takes no action, the corresponding channel controller degrades the data to achieve the required QoS.
As described above, the related art has disclosed methods for adjusting several QoS parameters according to the channel state. However, the disclosed related art methods include only independent adjustment of the QoS parameters according to the channel state, and do not provide yet a technique of optimizing a network bandwidth by synthetically considering the requirements of various client applications.